Electrophotographic imaging involves the development of toner onto a latent electrostatic image formed on the surface of a photoconductor. In electrophotographic printing, the latent electrostatic image is developed by selectively discharging the surface of the photoconductor using a laser. In both electrostatic copying and electrostatic printing, toner stored in a reservoir is supplied to a developer used for developing the electrostatic image.
Near the time useable amounts of toner from the reservoir have been consumed, the print quality can be degraded. Without a device for determining the amount of toner remaining in the toner reservoir, the electrophotographic imaging system can generate output that will be discarded because of unacceptable print quality. Furthermore, if the electrophotographic printer uses a cartridge containing the toner, the inability to determine the level of toner remaining in the cartridge can result in prematurely discarding the cartridge. Therefore, a need exists for a device that will allow accurate detection of the amount of toner in the reservoir of an electrophotographic imaging device.